From SOFAWiki

How to export a VisualModel to the Wavefront OBJ in SOFA

From the GUI

• Right click on a Node containing an instance of a OglModel component (or a component which derives from sofa::component::visualmodel::VisualModelImpl.
• Select "ExportOBJ"
• It wil provide an obj file representing the OglModel with the obj "yourscenename_00000.obj" along with a material file "yourscenename_00000.mtl"
• The files reside in the same directory as your SOFA scene.

This is the XML file which generated the example. You need to adapt it using the appropriate loader, and filename.

<Node  >
     <MeshSTEPLoader name="loader"  filename="STEP/moteur/Accessoire_moteur.stp"  deflection="0.1"  debug="0"  keepDuplicate="1" />
    <MeshTopology src="@loader" />
    <OglModel src="@loader" />
</Node >

Using the OBJExporter component